gas mileage- 80 -deville.

[1LowDeville]

as some know - my cat convert blew i already know i need to replace that . My plugs and wires look a little due for replacement - (no i haven't taken the plugs out observation) im just curious what the gas miles per tank was from full to empty-

2wks ago wednesday i filled up at 2.19 a gallon ($ 53.00 ) and i got gas again at 190 miles on the trip - now - i wasn't totally empty but a notch to being empty .. is my m.p.g that crappy in this car or its average for this car? i know i have a v8 motor but dang i didn't know it'd be this bad .. My aunt asked me how the car was running - i said its not she said why not ? i said cause i'm out of gas - Matter fact ran out of gas in the driveway - won't start til i get 1 gallon or more of gas , i must of drove home on fumes the last time i drove it . when i told her that i had 53 in gas like a week prior she was like god . MAYBE buying this caddy was a bad thing for me .Don't get me wrong i LOVE this car - drives like a dream not beat on sense it was owned by a old man . seems to me if i get 190 miles out of a tank of gas i would average 2 fillups if not more a week If i drive more then 190 miles. .. ( i can easily drive 300 miles or more a week i live in the boons nothing around here to do - i would have to drive out -to delaware which i could easily rack up 60 miles round trip) 53 X2 = 106$ A Week and if i have to fill 3times a week eek - 159$ ouch it would make it pointless to own the car - i 'd never have a job that would pay enough to pay bills and feed this car with fuel .. I WOULD rather not get rid of the car being as i just bought it and i really like it - any suggestions are greatfuel.

i am currently looking for work and it will appear to find a job that pays anything i'd have to drive to delaware really - or some where 60- miles or so 1 way- im a little concerned about m.p.g on this tank of gas .

obviously i need to do the cat -converter .

tuneups help but its not a major factor for a m.p.g issue.

I 'll have to look thru the paper work and see when the last actual tune up was done ( if i can read mechanics scribble is that some type of code they use so you don't know what they've done to your car ) well my mechanic has moved up in tech and gone computerized for his bills. atleast i can read and retype what is said to have been done

suggestions :

[BodybyFisher]

A rough calculation estimates that you are getting about 8 miles to the gallon. You didnt state how big your tank was. I took $53.00 divided by $2.19 and got 24.2 gallons. So it appears you have a 25 gallon tank. The Cadillac info I have states this > Fuel tank: 20.6 gal. (25 gal. available). I assume you have a 25 gallon tank. So if you divide 190 miles by 24 gallons you get 7.91 miles per gallon. That is a guesstimate... Don't assume that a tune up won't help, if you are running with burned poorly gapped plugs, bad ignition wires, etc that will hurt gas mileage. My 1974 Eldorado 500 cu in did better than that. Check the air in your tires, run them hard. Check timing it might be retarded. I looked for what the fuel consumption spec was but could not find it, my guess is that 14 local is a reasonable figure, but don't quote me..

[1LowDeville]

A rough calculation estimates that you are getting about 8 miles to the gallon. You didnt state how big your tank was. I took $53.00 divided by $2.19 and got 24.2 gallons. So it appears you have a 24 gallon tank. The Cadillac info I have states this > Fuel tank: 20.6 gal. (25 gal. available). I assume you have a 25 gallon tank. So if you divide 190 miles by 24 gallons you get 7.91 miles per gallon. That is a guesstimate... Don't assume that a tune up won't help, if you are running with burned poorly gapped plugs, bad ignition wires, etc that will hurt gas mileage. My 1974 Eldorado 500 cu in did better than that. Check the air in your tires, run them hard. Check timing it might be retarded. I looked for what the fuel consumption spec was but could not find it, my guess is that 14 local is a reasonable figure, but don't quote me..

well in my thread titled newb - i stated that my tires are " new" with 7k on them (well little more now that i got it ) when i bought the car - they are 7 years old - and were driven roughly around 1k a year in the last 7 years . I'll look around and see if i find a tire gauage somewhere here and check pressure- the p/o was pretty good with maintence on this car- he spent alot of money on repairs. i do intend on doing wires and plugs- think the cap ( do these have rotary buttons in them that need replace time to time ?) i'm used to chevy 4.3 motors and thier distriburators lol . ( have plenty experience swapping out the cap on that thing.) hmm i'll have to see what i can do about checking the timing on this - anyone know what the correct timing is for this car ?

[JasonA]

If your converter is still plugged, that could certainly hurt mileage.

To add to what BodyByFisher wrote (and airing the tires up to 35 psi is a good idea), go ahead and change the plugs with the correct ACDelco plugs for your car. Wires couldn't hurt either, especially if they don't look great or you don't know how old they are. A rotor and cap are probably not necessary, but you can inspect to see. Don't forget the air filter.

I would start with the catalytic converter, and THEN plugs and the air filter and go from there. At this point, your converter is probably hurting you more than anything. Don't just gut it out - do the right thing and get a new one on there. You can get a universal converter for cheap - less than 100 bucks - and have it installed by an exhaust shop.

I would expect you should be able to get at least 15 mpg in the city in that car. Perhaps closer to 18-20 if you drive it on the highway all the time. The proper way to determine your mileage will be to take the miles driven since your last fillup (you said 190 in this case) and divide that by how many gallons it took to fill. Don't go by "miles per tank" because that's not really accurate. Look at the gas dispenser and see exactly how many gallons it took.

If it truly did take 24 gallons to drive 190 miles, that's less than 8 mpg as BodyByFisher said. That's definitely too low, and something is wrong.

[PAUL T]

2wks ago wednesday i filled up at 2.19 a gallon ($ 53.00 ) and i got gas again at 190 miles on the trip - now - i wasn't totally empty but a notch to being empty .. is my m.p.g that crappy in this car or its average for this car?

How much did you put in when you "got gas again at 190 miles"? My guess would be that you went 190 miles on 3/4 of a tank. If your tank holds 25 gallons you probably used 18-19 gallons. I would say that you got 10+/- MPG. Before you replace anything (except the Cat Con) you need to check the Plugs for color and gap, air filter (hold it up to the sun and see if it shines through), plug wires for arcing (get a mist water bottle and spray the wires at night and watch for a light show), Rotor cap for carbon tracks, etc.. These things do not cost money to check, it just takes time. It sounds like time is what you have if you are bored with nothing to do in the boons and no job. Get in there and get your hands dirty. Why go to a mechanic for these little things? I would not expect to average much more than 15 MPG though. A Mazda pick-up it is not.

[Cadillac Jim]

The EPA records for 1980 are on this page:

http://www.fueleconomy.gov/feg/epadata/80guide.txt

Poking around a bit, I found the details: 14 city, 21 highway, 16 overall. If you are getting under 10 mpg, you need a tune-up.

You should expect about 16 mpg overall, with a reasonably light foot, which translates to 320 miles for 20 gallons. If you fill up when it gets below 1/4 tank with a 24-gallon tank, you should put in about 20 gallons or a little less.

[mmarinov]

The EPA records for 1980 are on this page:

http://www.fueleconomy.gov/feg/epadata/80guide.txt

Poking around a bit, I found the details: 14 city, 21 highway, 16 overall. If you are getting under 10 mpg, you need a tune-up.

You should expect about 16 mpg overall, with a reasonably light foot, which translates to 320 miles for 20 gallons. If you fill up when it gets below 1/4 tank with a 24-gallon tank, you should put in about 20 gallons or a little less.

Hmm, not too bad @ 16 mpg. Something must be amiss, 1Low. Although I must say, in my '79 T-Bird (351 Windsor, lead-ish foot) I got 4-6 mpg

That didn't last long!!

[1LowDeville]

thanks for the quick responses . ya i do do some shade tree mechanics . but i do not however own a timing gun .. i 'm willing to do the plugs and wires and perhaps the cap and button myself .. i do think my main issue IS that cat - i have been lookin online and i found one some where for 56$ and it was bolt in - i'd imagine it still needs a pro to install being as its the o.e.m and may give alot of headaches for someone who's layin on thier back in the drive way lol . easier with a torch

i'll find a tire gauage here and look and see what i get ..tires really don't look "UNDER pressure" tho.

another noticing before any this happend - i noticed the valve cover gaskets are leaking - not bad but they need new ones . neighbor and i are gona take care of that too when i get some chedda . (ha sorry had to say chedda )

so on my list of things to do :

replace cat .

check filter

check plugs

check wires

check tire pressure.

check timing??

[PAUL T]

Most of the time I have been on my back under the car working on the exhaust, the bolts are usually so rusty they break off. Sometimes I had to use a cold chisel or a hacksaw. Of course, I usually ended up with a few bloody nuckles though. By working on it yourself you not only save a few bucks but you gain so much more in experience. I made my share of mistakes but that was how I learned.

[The Fred]

I bet that the air filter is plugged,

Also clean your intake with intake cleaner.

Change the darned plugs they're a buck or two each

Change the darned wires

Tire pressure can impact mileage more than you think-

you can't tell by the look of the tire,

and don't use a cheap pencil gauge

My '79 with the 425 will do 12 in the city with the horrible misadjusted Q-Jet... That tells me that you should be getting 15+ with your foot out of it. If I drive like I drive in the '79, it only gets about nine city or less and much less than nine on the highway wide open.

PS:

Buy a bicycle.

[1LowDeville]

I bet that the air filter is plugged,

Also clean your intake with intake cleaner.

Change the darned plugs they're a buck or two each

Change the darned wires

Tire pressure can impact mileage more than you think-

you can't tell by the look of the tire,

and don't use a cheap pencil gauge

My '79 with the 425 will do 12 in the city with the horrible misadjusted Q-Jet... That tells me that you should be getting 15+ with your foot out of it. If I drive like I drive in the '79, it only gets about nine city or less and much less than nine on the highway wide open.

PS:

Buy a bicycle.

the fred

lets not start up again - the buy a bicycle wasn't nessarry to say - if you want to start throwin verbal punches back and forth simply cause i rubbed you the wrong way in my newbie thread tuff- live with it - if you can't obid by the mod's rules and listen to what they said then you should stop and leave- im not trying to start nothing here - i posted this thread for help and im asking for it and so far gotten good response til you had to ad your 2cents . don't destroy another thread i make - i didn't say nothing to you to start in this one . knock it off .

ps. if you continue your ignorant postings that are not related to topic and baiscally punches at me i WILL leave this forum - i came here for advise not to be bashed for my views on vehicles and what i do to vehicles .I understand this forum is open discussion and everyone has an opinion . You may not like me but i feel this theary is true : Opinions are like @ss holes ,everyone has 1 . if you don't have nothing good to say keep it to your self. (insert smiley middle finger here)

[BodybyFisher]

1Low try to ignore members that bother you. Me saying that is like the kettle calling the frying pan black I know, but its the best prescription. This member has complaints being lodged against him from across the Atlantic Ocean. In your My Controls you will find an IGNORE USER function.

Besides that, I think you have a good start at improving your gas mileage. Check your EGR valve also and all vacuum hoses. I don't know your car well does it set computer codes? Do you need a code scanner to determine codes or is it pre-computer code setting?

You really can't go by the look of your tires, run them hard, the car will handle better also, I would start at 34 / 35 cold try to keep the stagger front to rear (see inside of door for tire pressure).

[Texas Jim]

Ilowdeville,

I had an '80 DeVille. Around town, which is a lot of freeway, usually got around 15 to 17mpg. On the road taking a trip, if I would keep it below 80-85 ... would get around 20mpg, sometimes a tiny bit over that.

Put 225,000 miles on it before I sold it. It was a very good car and that 368 is a real tough engine. Never had a wrench on it except for 1 water pump and 1 set of valve cover gaskets. Just put gas in it, change the oil and drove the dickens out of it. Still didn't use any oil between changes when I sold it.

[1LowDeville]

1Low try to ignore members that bother you. Me saying that is like the kettle calling the frying pan black I know, but its the best prescription. The member in question has worn out his welcome, and has complaints being lodged against him from across the Atlantic Ocean. In your My Controls you will find an IGNORE USER function.

Besides that, I think you have a good start at improving your gas mileage. Check your EGR valve also and all vacuum hoses. I don't know your car well does it set computer codes? Do you need a code scanner to determine codes or is it pre-computer code setting?

You really can't go by the look of your tires, run them hard, the car will handle better also, I would start at 34 / 35 cold try to keep the stagger front to rear (see inside of door for tire pressure).

OK-

sense i ran out of gas in my drive- neighbor lent me 5$ i walked to the store got 2gall of gas and put it in - got a jump box and got it running ( yes i ran the battery down the other day ) it runs again . this cat needs replaced asap cause when i went to shut it off it kept desieling again then gave a light show underneath the car- and made a big ole bang -( reference "UNCLE Buck" movie neighbors ain't gona like that for long - and i will endup in trouble some time soon i'd expect . time to hunt down a converter.

[mmarinov]

/snip.../

it kept desieling again then gave a light show underneath the car- and made a big ole bang - neighbors ain't gona like that for long - and i will endup in trouble some time soon i'd expect . time to hunt down a converter.

This piqued my interest - what was the light show (sparks, red-hot exhast)?!?!

[BodybyFisher]

After hearing the backfire and dieseling (run on), check your ignition wires for proper routing and arching. Make sure they are not bundled together. Check your distributor cap for carbon tracking and cracks between the towers and between the tower and the center..

[Texas Jim]

OK-

sense i ran out of gas in my drive- neighbor lent me 5$ i walked to the store got 2gall of gas and put it in - got a jump box and got it running ( yes i ran the battery down the other day ) it runs again . this cat needs replaced asap cause when i went to shut it off it kept desieling again then gave a light show underneath the car- and made a big ole bang - neighbors ain't gona like that for long - and i will endup in trouble some time soon i'd expect . time to hunt down a converter.

1lowdeville

If it is dieseling when you shut it off, check the "anti diesel / idle speed solenoid" on the drivers side of the carb. With key off it should NOT be touching the carb linkage. Watch it and have someone turn on the ignition and it should pop out and touch the linkage and move it juat a TINY bit. Turn the key off and it should pull completely away from the linkage and let the butterflys close completely to prevent dieseling. Never had any trouble with my '80, but had to replace the one on the wifes '84 Fleetwood.

[1LowDeville]

The EPA records for 1980 are on this page:

http://www.fueleconomy.gov/feg/epadata/80guide.txt

Poking around a bit, I found the details: 14 city, 21 highway, 16 overall. If you are getting under 10 mpg, you need a tune-up.

You should expect about 16 mpg overall, with a reasonably light foot, which translates to 320 miles for 20 gallons. If you fill up when it gets below 1/4 tank with a 24-gallon tank, you should put in about 20 gallons or a little less.

so you think i could get that 320 mile range fuel economy after i fix the converter and change plugs and wires?? thats great- that would be alot better .

[1LowDeville]

/snip.../

it kept desieling again then gave a light show underneath the car- and made a big ole bang - neighbors ain't gona like that for long - and i will endup in trouble some time soon i'd expect . time to hunt down a converter.

This piqued my interest - what was the light show (sparks, red-hot exhast)?!?!

red spark i'd imagine - as i was in the car tryin to get it to shut off- neighbor saw it - i'll ask what color it looked like -

[Ranger]

There is no doubt that you will get milage back when you fix whatever is wrong. Like BBF, I got 13 mpg out of a 501 cid '73 Eldo. I can't imagine that plugs & wires would cause that big of a drop, though they certainly would contribute. Since this is a carburated engine, air filter condition will definately have an effect. A stuck or perferated float will also cause a rich condition. This could be a combination of several factors, all of which need to be brought into specs to get the milage back.

[JasonA]

The fact that the catalytic converter may be plugged/toast may indicate that there's something seriously wrong with the tune of the engine (rich) to cause that. Like Larry said, perhaps a physical malfunction with the carburetor. Few things will burn up a cat, but consistently running way rich will certainly do it.

[1LowDeville]

ya but what is the lifespan of a converter? this one appears to be the oem one and if so it would be 26 years old .

[BodybyFisher]

ya but what is the lifespan of a converter? this one appears to be the oem one and if so it would be 26 years old .

I don't think there is any lifespan per-se, they just go bad and rust internally or just clog from rusting and collapsing. In the old days, the Cadillacs used a 3 foot long resonator that used to rust and collapse and block the exhaust exit, I had that happen to me at college.

You can buy a backpressure gage and see if you are getting back pressure by screwing the gage into the pre-cat O2 sensor, but i don't think you have an O2 sensor. You could disconnect the Cat and see if the car runs better. What bothers me is the flashes you are getting under the car, is the muffler system open or damaged so that it will allow a back fire to escape and flash?

My wife has a 2002 Monte Carlo and the CAT has been replaced already but in 2002 GM bought inferior CATS from a supplier, and it was replaced under warranty.

[1LowDeville]

well my muffler is new - and it still gets exhaust out the tail reguardless of this problem - but when i hit the cat from under neath the car when its cold i get a dust like that comes out kinda like a accordian when you push it to gether it blows out the dust like - it will blow the dust like stuff out when first started til it runs a while - but i 'm still bettin the cat is clogged- . there is no damage to any other parts of my exhaust as far as i can see

here's another question . The old man i bought it from said don't hit the gas when you go to start it - you don't have to . Well - i tried that method when i was home - as you could see in my pics of my car i have a incline of a drive way- I back my car in as its easier for me to get out the drive and not get hit - i find cause i am parked on this incline that i have to press the gas a couple times to get it started- is this common or am i gona be forced to park my car in the street where its level ground ?? i rather not park my car in the street as ppl drive thru here like idiots . and in the winter we have a mandatory all streets clear when it snows . So i would have to park it in the drive way- i dunno if i can convience my community to dig up my drive way and make it level simply cause the car doesn't like starting without a couple pumps on the gas to start.. but like i said if im parked on a level ground i don't even have to touch the gas-

i dunno what to think.

[The Fred]

Alright I offended you, did you give a basic tuneup as I've suggested..?

That will need to be done and it will pay for itself no matter what.

If you had to borrow a fiver for gasoline and you won't work,

I really do think a Bicycle would serve you well..

I don't mean to offend you at all-

I just hate to think of you stranded and confused out in the middle of god knows where when it is so cold outside

I'll worry about my obiding you worry about getting this problem fixed and that darned tunep done! I know what it is to be low on cash, believe me, but if you don't maintain your car it will suck down all of your gasoline money in a hurry... !